Pitting / spalling

The contact face of the chilled cast iron followers appears to be damaged by micro pitting (left) respectively progressive pitting sometimes called spalling (right). The measured hardness of the surface is 52 HRC. Pitting is a surface fatigue phenomenon occurring in the presence of rolling and combined rolling with sliding. Damage occurs after a large number of load cycles, the so called incubation period.  Traction forces significantly affect the level of material stresses and thus the life duration

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